Not all sports cars get shitty mileage.
My 2002 Corvette Z06 gets a combined 24MPG, and routinely hits 28-30MPG on long freeway trips. My previous Vette, a 2000 Z19 hardtop, averaged 25MPG, and got 33MPG on a trip from Phoenix to Minneapolis.
Both of the cars have 5.7L V8 motors and 6-speed manual transmissions. The Z gets worse mileage not because of the extra 50HP/TQ, but because it is geared shorter (roughly 250-350RPM higher at any speed in any gear).
I'm not claiming either car is excellent for fuel economy, but you can't say sports cars should be lumped in with trucks when it comes to fuel economy. Just because none of the import sports car makers have figured out how to make a lot of power and get decent mileage, is no reason to badmouth all sports cars. Qualify your statements.